European Surface Waters Research Articles

Propanil impairs organ development in zebrafish by inducing apoptosis and inhibiting mitochondrial respiration

Propanil, an anilide herbicide, has frequently been detected in surface waters in Europe and the United States, largely due to its use in paddy cultivation areas. Particularly in specific regions like Sri Lanka, propanil is considered a potential cause of certain diseases and toxicities due to its high environmental runoff; however, there has been little research on its developmental toxicity. In the present study, we confirmed the developmental toxicity of propanil in zebrafish embryos exposed to 0, 2, 5, and 6 mg/L based on the LC50 value. Propanil exposure in embryos induced morphological changes, including decreased body length and eye size, and increased the heart and yolk sac edema. It increased the number of apoptotic cells in the brains and eyes of zebrafish larvae by 214 % and 184 %, respectively. Propanil-treated embryos exhibited altered mitochondrial metabolism, reducing basal respiration by 28 %, maximal respiration by 24 %, and ATP production by 38 %. These alterations induced organ defects in transgenic zebrafish models (cmlc2:DsRed, flk1:EGFP, olig2:DsRed, lfabp:DsRed;elastase:EGFP, and insulin:EGFP). It induced cardiovascular toxicity, as confirmed by the reduced atrial area, cerebrovascular intensity, and intersegmental vessels. Additionally, propanil decreased the fluorescence intensity of neurons, liver, and pancreas. Collectively, this study indicates that propanil causes early developmental toxicity through apoptosis and mitochondrial dysfunction. It presents a new perspective on how mitochondrial dysfunction, previously unreported in toxicity studies of other anilide herbicides, may affect developmental toxicity.

Drought impact on pharmaceuticals in surface waters in Europe: Case study for the Rhine and Elbe basins

Hydrological droughts are expected to increase in frequency and severity in many regions due to climate change. Over the last two decades, several droughts occurred in Europe, including the 2018-drought, which showed major adverse impacts for nature and different sectoral uses (e.g. irrigation, drinking water). While drought impacts on water quantity are well studied, little understanding exists on the impacts on water quality, particularly regarding pharmaceutical concentrations in surface waters. This study investigates the impact of the 2018-drought on concentrations of four selected pharmaceuticals (carbamazepine, sulfamethoxazole, diclofenac and metoprolol) in surface waters in Europe, with a major focus on the Elbe and Rhine rivers. Monitoring data were analysed for the period of 2010–2020 to estimate the spatiotemporal patterns of pharmaceuticals and assess the concentration responses in rivers during the 2018-drought compared to reference years. Our results indicate an overall deterioration in water quality, which can be attributed to the extremely low flow and higher water temperatures (∼ + 1.5 °C and + 2.0 °C in Elbe and Rhine, respectively) during the 2018-drought. Our results show an increase in the concentrations of carbamazepine, sulfamethoxazole, and metoprolol, but reduced concentrations of diclofenac during the 2018-drought. Significant increases in carbamazepine concentrations (+45 %) were observed at 3/6 monitoring stations in the upstream part of the Elbe, which was mainly attributed to less dilution of chemical loads from wastewater treatment plants under drought conditions. However, reduced diclofenac concentrations could be attributed to increased degradation processes under higher water temperatures (R2 = 0.60). Moreover, the rainfed-dominated Elbe exhibited more severe water quality deterioration than the snowmelt-dominated Rhine river, as the Elbe's reduction in dilution capacity was larger. Our findings highlight the need to account for the impacts of climate change and associated increases in droughts in water quality management plans, to improve the provision of water of good quality for ecosystems and sectoral needs.

Ecological Importance of Alkaline Phosphatase Activity and Acid Phosphatase Activity in Lakes with Different Catchment Use Structures

Surface waters in Europe and across other continents have been affected by anthropogenic activities, leading to changes in the ecological state of lakes due to the continuous phenomenon of eutrophication. This study assesses the activity of enzymes secreted in bottom sediments collected from two lakes, aiming to determine the interaction between bottom sediments and water based on samples collected from lake bottoms and overlying water. The study measured the production of secreted enzymes via alkaline phosphatase (ALP) and acidic phosphatase (ACP) in two distinct environments. Sample collection encompassed two lakes within two diverse catchment types (agroforestry and forest) during spring and summer. The findings revealed higher ACP values than ALP in both lake environments, with higher enzyme values recorded in the lake with a typical forest catchment area. High values of enzymes were related to the pollutant’s input into the lakes, suggesting that anthropogenic activities may have a substantial influence on the studied lakes. Principal component analysis (PCA) allowed the identification of a negative correlation between the enzymatic activity of phosphorus in bottom sediments and the content of organic phosphorus (org-P) in overlying waters only within the forest catchment, where the angle between the vectors representing primary variables is close to 180 degrees. The conducted statistical analysis demonstrated significant distinctions among the lakes concerning most of the examined parameters.

Comparative mitogenomics of native European and alien Ponto-Caspian amphipods

European inland surface waters are home to a rich diversity of native amphipod crustaceans, many of which face threats from invasive Ponto-Caspian counterparts. In this study, we analyse mitochondrial genomes to deduce phylogenetic relationships and compare gene order and nucleotide composition between representative native European and invasive Ponto-Caspian taxa across five families, ten genera and 20 species (with 13 newly sequenced herein). We observe various gene rearrangement patterns in the phylogenetically diverse native species pool.Pallaseopsis quadrispinosaandSynurella ambulansexhibit notable deviations from the typical organisation, featuring extensive translocations of tRNAs and the nad1 gene, as well as a tRNA-F polarity switch in the latter. The monophyletic invasive Ponto-Caspian gammarids display a conserved gene order, primarily differing from native species by a tRNA-E and tRNA-R translocation, which reinforces previous findings. However,Chaetogammarus warpachowskyishows extensive rearrangement with translocations of six tRNAs. The invasive corophiid,Chelicorophium curvispinum, maintains a highly conserved gene order despite its distant phylogenetic position. We also discover that native species have a significantly higher GC and lower AT content compared to invasive species. The mitogenomic differences observed between native and invasive amphipods warrant further investigation and could provide insights into the mechanisms underlying invasion success.

European-wide spatial analysis of sewage treatment plants and the possible benefits to nature of advanced treatment to reduce pharmaceutical emissions.

Pharmaceuticals are known to widely occur in the environment and to affect the health of ecosystems. Sewage treatment plants (STPs) are main emission pathways for pharmaceuticals, which are often not sufficiently removed during wastewater treatment. In Europe, STP treatment requirements are specified under the Urban WasteWater Treatment Directive (UWWTD). The introduction of advanced treatment techniques, such as ozonation and activated carbon, under the UWWTD is expected to be an important option to reduce pharmaceutical emissions. In this study, we present a European-wide analysis of STPs reported under the UWWTD, their current treatment level and potential to remove a set of 58 prioritised pharmaceuticals. Three different scenarios were analysed to show 1) UWWTD present effectiveness, 2) the effectiveness at full UWWTD compliance, and 3) the effectiveness when advanced treatment is implemented at STPs with a treatment capacity of >100.000 person equivalents. Based on a literature study, the potential of individual STPs to reduce pharmaceutical emissions ranged from an average of 9% for STPs with primary treatment to 84% for STPs applying advanced treatment. Results of our calculations show that European-wide emission of pharmaceuticals can be reduced with 68% when large STPs are updated with advanced treatment, but spatial differences exist. We argue that adequate attention should also be paid with regards to preventing environmental impacts of STPs with a capacity <100.000 p.e. Circa 44% of total STP effluent is emitted near Natura2000 sites (EU nature protection areas). Of all surface waters receiving STP effluent for which the ecological status has been assessed under the Water Framework Directive, 77% have a status of less than good. Relatively often only primary treatment is applied to wastewater emitted into coastal waters. This analysis can be used to further model pharmaceutical concentrations in European surface waters, to identify STPs for which more advanced treatment might be required and to protect EU aquatic biodiversity.

Use of random forest for assessing the effect of water quality parameters on the biological status of surface waters

The Water Framework Directive aims to reach good status in European surface waters by 2027. Despite the efforts taken already, the ecological status of surface waters has hardly improved during the last decades. In order to find efficient measures, there is an urgent need to improve our knowledge in understanding the linkage between the anthropogenic factors and the indicators of the ecological status assessment. Due to the complexity of the ecosystems, basic statistical methods (such as linear regression) cannot help in finding relationships between the biological quality elements and the supporting water chemistry parameters. The paper demonstrates that in these cases a machine learning data-driven method can be a promising tool for supporting biological classification. With random forest, the Gini index was used for ranking physico-chemical variables based on their influence on biological elements. Variables that have the biggest Gini index were selected for predicting the biological status of phytoplankton, phytobenthos and macrophytes. Binary classification and predictions were performed on a five-class scale. Predictions tended to be fairly good (errors varied within 8–60%, median 33.3%). A comparative analysis was also made with logistic regression, however, in some cases it led to slightly worse or slightly better predictions. We concluded that due to significant errors, the biological status assessment cannot be replaced completely by model predictions, but the method is sufficient to fill in certain gaps in the data and can help in the planning of biological monitoring systems. The evaluation was performed with Hungarian river and water quality database.

Novel approach for azole fungicides extraction from aqueous environments using terpenes and eutectic solvents

The presence of azole fungicides in aquatic environments is a significant issue due to their toxicity and persistence related to a low removal of these compounds by conventional processes in wastewater treatment plants. A growing environmental public concern is reflected in the inclusion of these compounds in the 2020 and 2022 European Surface Water Watch Lists. Therefore, it is necessary to develop efficient processes that allow their removal sustainably. This work applies liquid-liquid extraction using terpenes as green solvents and terpene-based eutectic solvents to remove azole fungicides from aqueous streams imazalil, metconozale, penconazole, prochloraz, and tebuconazole. First, an initial screening was performed by molecular simulation using the COSMO-RS method. The selected solvents were applied in the individual extraction of azole fungicides, and selecting the solvents thymol+octanoic acid and carvacrol. These solvents have been tested in studies with surface water matrix on the effect of temperature, initial concentration, and pH on extraction performance. From these results, it has been shown that carvacrol is the solvent that is least affected by these variables and obtains extraction yields higher than 97.88%, with a Solvent/Feed ratio up to 0.050, outperforming the conventional solvent methyl isobutyl ketone. This solvent has been used in solvent reuse cycles obtaining a reduction of less than 1% in three extraction cycles. Therefore, carvacrol is presented as a sustainable solvent for the extraction of azole fungicides from aqueous environments.

Strategic routes for wastewater treatment plant upgrades to reduce micropollutants in European surface water bodies

The European Union is determined to address the problem of contaminants of emerging concern (CEC) occurrence in natural water bodies. However, if a broad range of possible advanced treatment technological solutions exists as well as a variety of possible future conditions, then emission and consequently strategies for wastewater treatment plan (WWTP) upgrade and operation are not easy to anticipate. Here, a strategic foresight exercise was carried out to support decision-making matching anticipated future conditions toward the goal of finding suitable treatment upgrades to control CECs release in the environment. As a result, a roadmap and strategic routes were developed based on the interpretation of drivers for the EU region in the context of Shared Socioeconomic Pathways (SSPs) global change narratives. Screening and ranking of WWTP tertiary and advanced treatment technology upgrades were performed. Analysis of the resulting envisioned strategic routes allowed identifying and confronting core challenges such as the CEC removal agenda, technologies’ performance, requirements for CEC removal and water scarcity. The results also underline opportunities to shape WWTP technological upgrade planning such as: enhancing circular economy solutions in WWTP, water reclamation, and accelerated increase of the technology readiness level of hybrid and nature-based solutions.

From national monitoring to transnational indicators: reporting and processing of aquatic biology data under the European Environment Agency’s State of the Environment data flow

Biological monitoring data from aquatic ecosystems are collected from European countries on a yearly basis by the European Environment Agency (EEA) through the Water Information System for Europe (WISE). The WISE-SoE (State of Environment) data flows provide indicators of pressures, states and impacts of surface waters and groundwaters on a pan-European scale. The WISE-2 Biology was established to obtain a harmonised flow of biology data reported annually as Ecological Quality Ratios (EQRs) from European surface waters, as a supplement to the mandatory 6-yearly reporting of ecological status of water bodies for the Water Framework Directive. The purposes of this paper are 1) to describe the compilation of national aquatic biology monitoring data indicators and to inform about the public availability of these data, 2) to give an overview of the reported data and indicate the potential for assessments based on these data, and 3) to illustrate the potential for further use of the underlying species abundance data in biodiversity research and assessment. WISE-2 data are reported for the following biological quality elements: phytoplankton, phytobenthos, macrophytes, macroalgae, angiosperms, benthic invertebrates and fish in rivers, lakes, transitional and/or coastal waters. The EQR values represent the deviation from reference conditions. The final processed and quality-checked data are published in EEA’s database Waterbase - Biology, which currently holds data from more than 13,000 waterbodies in 26 countries from the reporting years 2011–2021. Examples of time series aggregated by geographic regions give an indication of the type of trends that can be obtained from the reported data at the nEQR scale. However, the current results are representative only for certain geographic regions with high coverage of water bodies. Within the European research project EuropaBON (Europa Biodiversity Observation Network), the use of WISE-2 data can be leveraged to support biodiversity policy and conservation planning. EuropaBON’s online database provides an overview of how biodiversity monitoring schemes across Europe flows through different integration nodes, to produce Essential Biodiversity Variables and other policy-relevant indicators. Here, we use the EuropaBON visualisation tool to illustrate the WISE-2 as a European integration node for 157 biology datasets via the national integration nodes.

Resilience of barley (Hordeum vulgare) plants upon exposure to tramadol: Implication for the root-associated bacterial community and the antioxidative plant defence system

Insufficiently treated reclaimed water can act as a source of contamination by introducing recalcitrant contaminants (e.g., pharmaceutical compounds) to various water bodies and/or agricultural soils after irrigation. Tramadol (TRD) is one of these pharmaceuticals that can be detected in influents and effluents of wastewater treatment plants, at discharge points as well as in surface waters in Europe. While the uptake of TRD by plants through irrigation water has been shown, plant responses towards this compound are still unclear. Therefore, this study aims to evaluate the effects of TRD on selected plant enzymes as well as on the root bacterial community structure. A hydroponic experiment was conducted to test the effects of TRD (100 μg L−1 TRD) on barley plants, at two harvesting time points after treatment. Accumulation of TRD in root tissues over time was observed reaching concentrations of 111.74 and 138.39 μg g−1 in total root FW after 12 and 24 days of exposure, respectively. Furthermore, noticeable inductions in guaiacol peroxidase (5.47-fold), catalase (1.83-fold) and glutathione S-transferase (3.23- and 2.09-fold) were recorded in roots of TRD-treated plants compared to controls after 24 days. A significant alteration in the beta diversity of root-associated bacteria due to TRD treatment was observed. Three amplicon sequence variants assigned to Hydrogenophaga, U. Xanthobacteraceae and Pseudacidovorax were differentially abundant in TRD-treated compared to control plants at both harvesting time points. This study reveals the resilience of plants through the induction of the antioxidative system and changes in the root-associated bacterial community to cope with the TRD metabolization/detoxification process.

Updating the Chronic Freshwater Ecotoxicity Database and Biotic Ligand Model for Nickel for Regulatory Applications in Europe.

Bioavailability has been taken into account in the regulation of nickel in freshwater ecosystems in Europe for over a decade; during that time a significant amount of new information has become available covering both the sensitivity of aquatic organisms to nickel toxicity and bioavailability normalization. The ecotoxicity database for chronic nickel toxicity to freshwater organisms has been updated and now includes 358 individual data points covering a total of 53 different species, all of which are suitable for bioavailability normalization to different water chemistry conditions. The bioavailability normalization procedure has also been updated to include updates to the bioavailability models that enable more sensitive water chemistry conditions to be covered by the model predictions. The updated database and bioavailability normalization procedure are applicable to more than 95% of regulated European surface water conditions and have been used to calculate site-specific criteria for a variety of different water chemistry scenarios, to provide an indication of how the sensitivity to nickel varies between different water types. The hazardous concentration for 5% of a species (HC5) values for this diverse selection of water types range from 1.6 to 36 µg L-1 , clearly demonstrating the importance of accounting for nickel bioavailability in freshwaters. This updated database and bioavailability normalization procedure provide a robust basis for the derivation of regulatory thresholds for chronic nickel toxicity in freshwaters such as predicted no-effect concentrations and Environmental Quality Standards and are protective of the results of several mesocosm studies. Environ Toxicol Chem 2023;42:566-580. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

An environmentally relevant concentration of antibiotics impairs the immune system of zebrafish (Danio rerio) and increases susceptibility to virus infection.

In this work, we analysed the transcriptome and metatranscriptome profiles of zebrafish exposed to an environmental concentration of the two antibiotics most frequently detected in European inland surface water, sulfamethoxazole (SMX) and clarithromycin (CLA). We found that those animals exposed to antibiotics (SMX+CLA) for two weeks showed a higher bacterial load in both the intestine and kidney; however, significant differences in the relative abundance of certain bacterial classes were found only in the intestine, which also showed an altered fungal profile. RNA-Seq analysis revealed that the complement/coagulation system is likely the most altered immune mechanism, although not the only one, in the intestine of fish exposed to antibiotics, with numerous genes inhibited compared to the control fish. On the other hand, the effect of SMX+CLA in the kidney was more modest, and an evident impact on the immune system was not observed. However, infection of both groups with spring viremia of carp virus (SVCV) revealed a completely different response to the virus and an inability of the fish exposed to antibiotics to respond with an increase in the transcription of complement-related genes, a process that was highly activated in the kidney of the untreated zebrafish after SVCV challenge. Together with the higher susceptibility to SVCV of zebrafish treated with SMX+CLA, this suggests that complement system impairment is one of the most important mechanisms involved in antibiotic-mediated immunosuppression. We also observed that zebrafish larvae exposed to SMX+CLA for 7 days showed a lower number of macrophages and neutrophils.

Recent regional changes in nutrient fluxes of European surface waters

We have quantified inputs and fate of nutrients in European fresh and marine waters from 1990 to 2018. We have used the conceptual model GREEN to assess the impact of efforts on curbing nutrient pollution in European regions. In the first two decades, i.e. in the 1990s and through the start of the new millennium, nutrient inputs to waters decreased significantly. Nutrient pollution in freshwaters and to the sea largely reduced in all regions, although at different pace. However, around 2008–2010 trends in nutrient inputs changed, marking an increase in the last decade, particularly from agricultural diffuse sources. In some regions, current nutrient inputs to waters are close to those estimated at the beginning of the 1990s. At the end of the study period, nutrient concentrations in freshwaters remain above thresholds congruent with good ecological status of water bodies in most downstream reaches. European policies tackling point sources are close to reach their maximum impact. In the face of this approaching ceiling, sustainable nutrient management on agricultural land becomes pivotal for effective nutrient control in river basins. The regional approach highlighted differences across Europe that may provide tailored opportunities to plan effective strategies for achieving environmental targets.

Biosensing Chlorpyrifos in Environmental Water Samples by a Newly Developed Carbon Nanoparticle-Based Indirect Lateral Flow Assay.

Pesticides are used in agriculture to prevent pests. Chlorpyrifos (CHLP) is an insecticide with potentially detrimental effects on humans, bees, and the aquatic environment. Its effects have led to a total ban by the European Union (EU), but outside the EU, CHLP is still produced and used. An indirect lateral flow immunoassay (LFIA) for the detection of CHLP was developed and integrated into a cassette to create a lateral flow device (LFD). Species-specific reporter antibodies were coupled to carbon nanoparticles to create a detector conjugate. Water samples were mixed with a specific CHLP monoclonal antibody and detector conjugate and applied to the LFD. Dose-response curves elicited the detection of low concentrations of CHLP (<1 µg/L). This sensitivity was recorded through a rapid handheld digital imaging device but also visually by naked eye. The CHLP LFD was applied to a range of European surface water samples, fortified with CHLP, revealing a sensitivity in these matrices of 2 µg/L, both by digital and visual analysis. To improve the simplicity of the CHLP LFIA, the assay reagents were dried in tubes, enabling to carry out the test by simply adding water samples and inserting the LFIA strips. This CHLP LFIA is thus suited for the on-site screening of surface waters.

A Preliminary European-Scale Assessment of Microplastics in Urban Wastewater

Microplastics (MP) are not well defined from an analytical point of view and their measurement in the environment is still challenging. At the same time, their increasingly widespread presence is raising concerns for human health and ecosystems. In this contribution, we present a preliminary European-scale assessment of the environmental input of MP through urban wastewater and urban runoff. We quantify the emissions associated with urban wastewater based on the range of observed concentrations in wastewater treatment plants (WWTPs) effluents, and the emissions from tire wear particles (TWP) by assuming that a percentage of the particles generated on roads eventually reaches surface waters. In spite of the large uncertainties entailed in the calculation, it is apparent that TWP dominate the input of total plastic loads into European surface waters. The management of urban runoff, road runoff, and combined sewer overflows (CSO) is essential to control the emissions of MP from urban areas. On the other hand, WWTPs retain the majority of MP in the sewage sludge. The spreading of sewage sludge onto soil therefore represents a potential pathway of MP from urban wastewater into the environment.

Variability of Nitrogen and Phosphorus Content and Their Forms in Waters of a River-Lake System

River-lake systems in Central Europe represent the majority of surface water system forms. In these systems lakes play an important role in river water quality. Published reports on the quality of surface waters in Europe indicate progressive deterioration of their quality, resulting mainly from increasing eutrophication. This study analyzed the content of two biogenic elements—nitrogen and phosphorus—and their mineral forms in the Głuszynka river, representative for the river-lake systems of Central Europe. The research was conducted in the hydrological years 2016–2018. The ecological status of the Głuszynka river, due to the “poor” status of both biological elements and physicochemical elements (content of phosphorus and nitrogen compounds), was classified as “poor.” In the period analyzed an increase in the content of nitrogen compounds was recorded in the hydrological year 2018. However, during the growing period a significant decrease in the content of total and nitrate nitrogen was observed, which was related to the activity of primary producers. For phosphorus compounds a slight increase of their content was observed during this period. This was associated with high tourist and recreational pressure on the analyzed system. Analyzing the spatial variability of biogenic compounds it was observed that along the course of the river the content of nitrite and nitrate nitrogen as well as total nitrogen increased at successive sampling points. An opposite trend of change along the river course was observed for phosphorus compounds (content of P-PO4 and total phosphate decreased by 14 and 15.9%, respectively). Statistical analyses carried out highlighted the relationship between water quality and land use in the direct catchments of lakes included in the river-lake network. Arable land was associated with higher the content of orthophosphorus phosphate, grassland total nitrogen, nitrite and nitrate nitrogen, while urbanization was strongly associated with ammonium nitrogen.

Environmental quality standards for diclofenac derived under the European water framework directive: 2. Avian secondary poisoning

Diclofenac is a nonsteroidal anti-inflammatory human and veterinary medicine widely detected in European surface waters, especially downstream from Wastewater Treatment Plants. With some notable exceptions, veterinary uses of diclofenac in Europe are greatly restricted, so wastewater is the key Europe-wide exposure route for wildlife that may be exposed via the aquatic environment. Proposed Environmental Quality Standards (EQS) which include an assessment of avian exposure from secondary poisoning are under consideration by the European Commission (EC) to support the aims of the Water Framework Directive (WFD). In this paper we summarise information on avian toxicity plus laboratory and field evidence on diclofenac bioaccumulation and bioconcentration in avian food items. A safe diclofenac threshold value for birds of 3 μg kg−1 wet weight in food was previously derived by the European Medicines Agency and should be adopted as an EQS under the WFD to maintain consistency across European regulations. This value is also consistent with values of 1.16–3.99 µg kg−1diet proposed by the EC under the WFD. Water-based EQS of 5.4 or 230 ng L−1 in freshwater are derived from these dietary standards, respectively, by the EC and by us, with the large difference caused primarily by use of different values for bioaccumulation. A simple assessment of potential water-based EQS compliance is performed for both of these latter values against reported diclofenac concentrations in samples collected from European freshwaters. This shows that exceedances of the EC-derived EQS would be very widespread across Europe while exceedances of the EQS derived by us are confined to a relatively small number of sites in only some Member States. Since there is no evidence for any declines in European waterbird populations associated with diclofenac exposure we recommend use of conservative EQS of 3 µg kg−1diet or 230 ng L−1 in water to protect birds from diclofenac secondary poisoning through the food chain.

Spatial distribution of the relationship between nitrate residues in soil and surface water quality revealed through attenuation factors

Thanks to the intense efforts over the past decades to reduce nutrient losses, the annual average nitrate (NO3-) concentrations in the European surface waters have decreased between 1990 and 2010, but the reduction has levelled off since then. Nitrogen (N) mitigation measures adapted to the local conditions are needed to further reduce the N pressure from agriculture on surface water quality. The NO3--N residue measured before the onset of winter has been used as a simple indicator of the N pressure from agriculture. However, the vulnerability of a stream to NO3- inputs depends on dilution and reduction of NO3- during its transport towards the surface water, which can be expressed by the attenuation factor for surface water (AFsw), i.e. the ratio of the average NO3- concentration at the bottom of the rooting zone and the average NO3- concentration in the surface water. In this study, we combined NO3--N measurements in the soil in autumn, NO3- concentrations measured in the surface water during the winter period and a relatively simple soil-crop model to calculate AFsw at subcatchment level, in order to estimate the effect of mitigation measures without collecting detailed information on the subsoil and groundwater processes. Simulations demonstrated that in Flanders (the northern part of Belgium) the further optimisation of the N fertilisation rate is the most effective measure to reduce surface water NO3- concentrations. Maximising the acreage of catch crops had a limited additional effect on the NO3- concentrations in surface water given that this is already widely practiced at present. Although the removal of N rich crop residues is highly effective at field level, it contributed little to the reduction of NO3- concentrations in the surface water because of the small acreage of these crops. The implemented scenarios show that in subcatchments with low AFSw, targeted and subcatchment-specific combinations of measures, but including the trade-off with the potential economic and other negative effects, may not be sufficient to obtain acceptable NO3- concentrations in the surface water at subcatchment level. In regions with low AFsw, end–of-pipe technologies might be more cost-effective and even imperative to avoid the risk of eutrophication and a low surface water quality.

Extraction of antibiotics identified in the EU Watch List 2020 from hospital wastewater using hydrophobic eutectic solvents and terpenoids

The increasing consumption of pharmaceuticals, along with the ineffectiveness of conventional wastewater treatment, has resulted in an increased presence of these pollutants in both drinking water supplies and aquatic environments. The potential adverse health effects and environmental impact of these chemicals are drawing the attention of several bodies around the world. For instance, some antibiotics such as ciprofloxacin, trimethoprim, and sulfamethoxazole have been included in the most recent European Surface Water Watch List under the EU Water Framework Directive (Decision 2020/1161). The present work proposes the use of terpenoids and eutectic solvents, as effective and green solvents with low toxicity, for multicomponent liquid–liquid extraction of ciprofloxacin, trimethoprim, and sulfamethoxazole from ultrapure water and hospital wastewater. The COSMO-RS method was used for a predictive initial solvent screening. Thymol, carvacrol, eutectic solvents (thymol + fatty acids), and conventional solvents (methyl isobutyl ketone and ethyl acetate) were selected to be used in the experiments. The influence of the volumetric S/F ratio, aqueous matrix, and pH was analysed. Conventional solvents show significantly lower overall extraction yields than those observed for eutectic solvents and terpenoids at any pH and matrix. Carvacrol presented the most favourable conditions, reaching overall extraction yields above 98.0% (98.9% for trimethoprim, 99.5% for ciprofloxacin, and 97.0% for sulfamethoxazole) with hospital wastewater at pH 5.0 and S/F ratio of 1.00. Carvacrol showed a feasible operation in a continuous extraction column at room temperature, providing effective reuse and regeneration processes in this study.

Molecular Probing of DOM Indicates a Key Role of Spruce-Derived Lignin in the DOM and Metal Cycles of a Headwater Catchment: Can Spruce Forest Dieback Exacerbate Future Trends in the Browning of Central European Surface Waters?

Peatlands of the Northern Hemisphere and Central European coniferous forests experience significant environmental change. The resultant browning of surface waters, that is, elevated concentrations of dissolved organic matter (DOM) and metals, is of interest in the context of the global C cycle, peatland and forest management, and water treatment. In an attempt to identify the causes of this process in the Harz Mountains (Central Germany), we studied the spatiotemporal variations in DOM molecular composition (thermally assisted hydrolysis and methylation combined with GC-MS) and metal concentrations in headwater stream samples. We found strong relationships between DOM and metals and seasonal variations in the DOM quality and tentatively DOM-metal binding mode: during summer base flow, DOM and metal concentrations are low, and all elements other than the alkali and alkaline earth metals (Ca, Mg, Sr, K, and Na) are positively correlated to DOM, whereas during spring and autumn (high discharge), only metals with strong affinity for DOM (Fe, As, Cu, Cr, Pb, and Ti), but not weakly binding ones (Al, Cd, La, Mn, Ni, Zn, and Zr), are correlated to DOM, indicative of selectivity in DOM-metal interactions. The products of polyphenols are the key ingredients of the DOM-metal complexes. We argue the importance of spruce lignin-derived vanillic acid moieties, which are involved in weak (all seasons) and strong, multidentate and/or colloidal, binding (spring and autumn) of metals. Considering the ongoing spruce forest dieback and climate change acceleration, it is tempting to conclude that spruce necromass and forest soils may release vast amounts of lignin-derived DOM and associated metals to headwater streams. This would have significant implications for forest soil C stocks and the management of connected drinking water reservoirs.